1. Field of the Invention
The present invention relates generally to medical drainage systems configured to remove bodily fluids from a patient, and more particularly, to a medical drainage system to controllably remove bodily fluids, such as cerebrospinal fluid (CSF), from a patient.
2. Brief Description of Related Art
Cerebrospinal fluid (CSF) is normally a clear watery body fluid that is formed by the human body in the ventricular cavities located within the brain. The CSF flows from the lateral ventricles and third ventricle to the fourth ventricle. Thereafter, the CSF under normal conditions exits the fourth ventricle to flow into the subarachnoid spaces that surround the outside of the brain, the spinal cord, and the lumbosacral nerve roots. The CSF under normal conditions forms at a rate of about 400-500 milliliters per day and is absorbed by the body at the exact same rate, such that the equilibrium between the formation of CSF and the absorption of CSF exists. This balance between the formation of CSF and the absorption of CSF prevents CSF from accumulating under pressure in the central nervous system. A rise in intracranial pressure (ICP) from the accumulation of excess amounts of CSF may lead to headaches, coma, or even death.
Accumulation of CSF above normal physiological levels may occur for a variety of reasons. Blockage of the flow of CSF may cause accumulation of CSF in the ventricles and a rise in ICP. Such blockages to the flow of CSF may result from tumors or may be associated with subarachnoid hemorrhage, for example when an intracranial aneurysm ruptures. Increased intracranial pressures may also occur in pseudotumor cerebri; a condition where more CSF is formed than is absorbed. Furthermore, increased ICP may be associated with infections such as meningitis.
External CSF drainage systems are typically used in a clinical setting when it is desirable to drain CSF through a catheter and into a “closed” collection system to prevent infection of the CSF that may result in meningitis. CSF drainage is desirable in the treatment of patients having increased intracranial pressure (ICP), a condition where the pressure of CSF or brain matter in the skull exceeds the normal upper physiological limits of pressure. External CSF drainage is also desirable to lower increased or normal ICP in patients with pathological CSF leakage from the nose (rhinorhea) or ears (otorhea) such as may occur with fractures of the base of the skull. Lowering the ICP frequently allows the fractures to heal and the leak to seal without more aggressive surgical intervention. External CSF drainage is also used in patients with hydrocephalus, a condition where CSF pathologically accumulates in the ventricles of the brain. Furthermore, external CSF drainage is used for temporary drainage when an internalized CSF shunt system fails or is infected.
Some conditions causing increased ICP may be treated by drainage of CSF. Surgical drainage of CSF may be performed by either a ventricular catheter, which is inserted into a lateral ventricle of a cerebral hemisphere, or by a lumbar drainage catheter, which is inserted into the subarachnoid space in the lumbar spine. These catheters allow for removal of excess CSF.
Removal of too much CSF, or “overdrainage,” by these catheters is also not desirable. Excessive CSF drainage by ventricular or lumbar catheters may result in severe headaches or collapse of the ventricular cavities. Collapse of the ventricular cavities may cause movement of the cerebral cortex inwardly, sometimes causing traction on veins that rupture and form subdural hematomas. Excessive collapse of the ventricles may also cause shifts of the brain and cerebral arteries, thereby causing re-rupture of an intracranial aneurysm. Measured drainage of the CSF through ventricular or lumbar drainage catheters is highly desirable. Furthermore, drainage of CSF through these catheters is preferably done in a closed system, for example a sealed bag, wherein the CSF has very limited exposure to microbes in room air. CSF is typically sterile when drained from the patient and contamination of the CSF by microbes may have adverse consequences on the patient.
Several drainage systems configured for the generally closed drainage of CSF from either the lumbar subarachnoid space or cerebral ventricles have been described. These drainage systems typically include tubing and one or more valves such as stopcocks to control the flow of CSF from the patient through the drainage catheter. These drainage systems also typically include a sterile bag or other type of container for collection of the CSF.
Clinicians generally wish to limit CSF drainage from the patient to a rate of about 10 milliliters to 50 milliliters per hour so that overdrainage does not occur. Overdrainage of CSF from the patient can result in “overfilling” of the drainage bag which is a condition wherein too much CSF fluid fills the drainage bag. Overfilling a drainage bag or container may cause further problems, including leakage of the fluid from the system and infection through the pathway provided by the leaking fluid.
Overfilling may also cause undesirable CSF contact with portions of a drainage system that function best when kept dry, for example an hydrophobic filter. In certain containers, such as a rigid-wall burette, a vent is required for filling the container and then also for draining the container. To maintain a closed system, a filter is typically located at the vent so that air may leave as the container is being filled and filtered air may enter as the container is being emptied. The vent filter is typically hydrophobic so that liquid within the container does not escape to the environment and liquid outside the container does not enter the container. The filter may also include an anti-microbial substance or it may antimicrobial due to the filter media pore size. Pore size less than three microns is considered to be antimicrobial as bacteria cannot pass through this aperture. CSF typically includes glucose and other proteinaceous substances and should CSF come into contact with a vent filter, it may adhere to the filter thereby making the passage of air through the filter in either direction difficult or impossible. The container would then be rendered useless and must be replaced. Therefore, in the case where a collection container having a vent filter is used for collecting CSF, it would be desirable to limit the amount of CSF flowing into the collection container so that the CSF does not contact the vent filter. Controlling the amount of CSF entering a container has been done in the past by clinicians closely visually monitoring the level of CSF in the container and when the amount reaches a certain level, closing a stopcock to prevent such complications from overdrainage and overfilling. Such monitoring requires the personal attention and time from clinicians who are probably already quite busy.
The flow rate of CSF in many drainage and collection systems is crudely controlled by the level at which the collection system is positioned above the head or spine of the patient being treated. Flow may unexpectedly increase if the level of the system is lowered in relation to the level of the catheter entering the patient. For example, an uncooperative or confused patient may sit up in bed, thereby changing his position farther above where the system has been positioned and result in an increased flow rate of CSF into the drainage and collection system. These systems may further result in overdrainage when the collection container is inadvertently positioned too low and/or drainage goes unnoticed by the busy clinician for some time. A more serious risk can occur when a displaced collection container falls or is compressed thereby forcing a large volume of the collected CSF back into the patient. Flow of CSF through a drain may also suddenly increase with coughing or sneezing by the patient. Excess drainage may also occur from siphoning phenomenon. Overfilling may occur if a busy clinician does not empty the collection chamber of CSF before it fills to undesirable levels. Therefore with these present systems, the amount of CSF flowing out of the patient must be closely monitored by a clinician to prevent complications from overdrainage and overfilling.
Medical drainage systems have been described in the art that include various types of flow or pressure regulating valve systems. The systems sometimes also include a vent system or antisiphoning mechanism. One device known in the art is an external ventricular drainage assembly that includes a ventricular drainage catheter placed in the ventricles of a patient's brain and which is connected to a suture tab for securing the catheter to the patient for preventing relative movement between the catheter and patient. A manually operated valve such as a stopcock is connected to the catheter for selectively opening and closing the external ventricular drainage assembly to fluid flow. An adapter is connected to the stopcock valve for providing access to the fluid flow path within the assembly. A one-way valve such as a miter valve having no moving parts is connected to the adapter. A first length of flexible tubing is connected to the one-way valve and is joined through a connector to a second length of flexible tubing. A collection reservoir is connected to the second length of flexible tubing and includes an entry and outlet port. A drip chamber is positioned between the second length of flexible tubing and the collection reservoir. This is a manually-controlled system as described above.
Another known device is a ventricular drainage system that includes an antisiphon device having a chamber configured for vertical inflow of CSF from the bottom of the chamber to the top of the chamber. An outflow tube is connected at the upper end of the chamber. The device also includes a freely floating ball in the chamber that is capable of closing the inflow tract at the bottom of the chamber when there is no flow of fluid from the ventricular catheter, capable of allowing fluid flow through the chamber during a normal flow of liquid from the catheter and capable of closing the outflow tract upon a rush of fluid from the catheter. Such a system does not account for overfilling.
Also known in the art is a drainage system having an in-line one-way valve for use in the drainage of ventricles of a patient's brain or of the patient's lumbar region and which is connected to a catheter inserted in either the ventricles or lumbar region and secured to the patient. The system includes tubing from the catheter, a four-way stopcock inserted into the tubing followed by a Y-connector providing a sampling site, and a low-pressure one-way valve in line with the tubing to help prevent reflux of fluid into the ventricles or lumbar subarachnoid space. A length of flexible tubing leads from the one-way valve to a burette clamped onto an IV pole, and a drainage bag connected to the bottom of said burette to receive the collected fluid from the burette after it is measured. This system also does not prevent overfilling and requires manual monitoring.
The above devices known in the art all have disadvantages when applied to clinical use for measured CSF drainage. For example, prior art devices do not provide an automatic limitation of flow, or they are complicated and expensive to manufacture, fill from the bottom, clog easily when exposed to proteinaceous fluids, or may hamper the free flow of CSF between a patient and a collection container.
Hence those skilled in the art have recognized a need for a drainage system that avoids conditions of both overdrainage and overfilling. What is needed is a system and method that limit the volume of CSF draining into a collection device such that the volume of drained CSF can be controlled, accurately measured, and configured so that a drainage collection container can be conveniently removed from the bottom of the collection chamber as required. A need also exists for a CSF drainage device that is inexpensive and disposable. There is a further recognized need for a CSF device that provides automatic shut off of fluid flow at a predetermined volume of drainage and which prevents overfilling so as to prevent CSF from coming into contact with a vent filter. The present invention provides solutions to these and other identified needs in the art.